/**
 * 求两个颜色之间的渐变值
 * @param {string} startColor 开始的颜色
 * @param {string} endColor 结束的颜色
 * @param {number} step 颜色等分的份额
 * */
function colorGradient(startColor = 'rgb(0, 0, 0)', endColor = 'rgb(255, 255, 255)', step = 10) {
  let startRGB = hexToRgb(startColor, false) //转换为rgb数组模式
  let startR = startRGB[0]
  let startG = startRGB[1]
  let startB = startRGB[2]

  let endRGB = hexToRgb(endColor, false)
  let endR = endRGB[0]
  let endG = endRGB[1]
  let endB = endRGB[2]

  let sR = (endR - startR) / step //总差值
  let sG = (endG - startG) / step
  let sB = (endB - startB) / step
  let colorArr = []
  for (let i = 0; i < step; i++) {
    //计算每一步的hex值
    let hex = rgbToHex('rgb(' + Math.round(sR * i + startR) + ',' + Math.round(sG * i + startG) + ',' + Math.round(sB * i + startB) + ')')
    colorArr.push(hex)
  }
  return colorArr
}

// 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
function hexToRgb(sColor, str = true) {
  let reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  sColor = sColor.toLowerCase()
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = '#'
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    //处理六位的颜色值
    let sColorChange = []
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)))
    }
    if (!str) {
      return sColorChange
    } else {
      return `rgb(${sColorChange[0]},${sColorChange[1]},${sColorChange[2]})`
    }
  } else if (/^(rgb|RGB)/.test(sColor)) {
    let arr = sColor.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')
    return arr.map((val) => Number(val))
  } else {
    return sColor
  }
}

// 将rgb表示方式转换为hex表示方式
function rgbToHex(rgb) {
  let _this = rgb
  let reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  if (/^(rgb|RGB)/.test(_this)) {
    let aColor = _this.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')
    let strHex = '#'
    for (let i = 0; i < aColor.length; i++) {
      let hex = Number(aColor[i]).toString(16)
      hex = String(hex).length == 1 ? 0 + '' + hex : hex // 保证每个rgb的值为2位
      if (hex === '0') {
        hex += hex
      }
      strHex += hex
    }
    if (strHex.length !== 7) {
      strHex = _this
    }
    return strHex
  } else if (reg.test(_this)) {
    let aNum = _this.replace(/#/, '').split('')
    if (aNum.length === 6) {
      return _this
    } else if (aNum.length === 3) {
      let numHex = '#'
      for (let i = 0; i < aNum.length; i += 1) {
        numHex += aNum[i] + aNum[i]
      }
      return numHex
    }
  } else {
    return _this
  }
}

/**
 * JS颜色十六进制转换为rgb或rgba,返回的格式为 rgba（255，255，255，0.5）字符串
 * sHex为传入的十六进制的色值
 * alpha为rgba的透明度
 */
function colorToRgba(color, alpha = 0.3) {
  color = rgbToHex(color)
  // 十六进制颜色值的正则表达式
  var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  /* 16进制颜色转为RGB格式 */
  let sColor = color.toLowerCase()
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      var sColorNew = '#'
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    // 处理六位的颜色值
    var sColorChange = []
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)))
    }
    // return sColorChange.join(',')
    return 'rgba(' + sColorChange.join(',') + ',' + alpha + ')'
  } else {
    return sColor
  }
}

export default {
  colorGradient,
  hexToRgb,
  rgbToHex,
  colorToRgba
}
